The present invention. relates to an improved filter cartridge, particularly for jug or carafe water purifiers, according to the preamble to the main claim.
The use of filtering systems with replaceable cartridges for cleansing the drinking water of organoleptically unpleasant odours and flavours is widespread.
Typically, activated-carbon filters are used and these have to be replaced after a predetermined number of filtering cycles. The cartridge contains a bed of activated carbon and in turn separates two compartments of a jug, for holding water to be filtered and filtered water, respectively.
To prevent the user from being able to use the same cartridge for a greater number of cycles than is compatible with effective operation of the cartridge, these filtering systems generally have counters which can block access to the jug to prevent new water from being admitted to the compartment for water to be filtered once the count indicates that the filtering capacity of the cartridge is probably exhausted.
The main disadvantage of these counter systems is that it is generally possible to zero the countermand clear the access to the jug without replacing the cartridge and thus to make further use of an exhausted cartridge.
Although this does not lead to any particular problems beyond inadequate purification of the water treated when the purpose of the system is limited to the cleansing of the water of unpleasant odours and flavours, clearly this system cannot be used with the necessary safety when the filtering cartridge is required to cleanse the water being treated of microbial and/or bacteriological loads, that is, when it is required actually to make the water drinkable.
In this case, it is essential for the flow of water through the filtering system to be prevented once and for all as soon as circumstances arise such that the filtering capacity of the cartridge should be considered to be exhausted, for example, after the treatment of a predetermined number of litres of water to be made drinkable. Otherwise, the user would be drinking not only inadequately deodorized water, but water which is potentially polluted by bacteria and other organisms or substances hazardous to health.
Valves or similar mechanisms capable per se of shutting off a duct after a predetermined flow has passed through it are known, for example, from U.S. Pat. Nos. 4,681,677, 3,586,018, 3,503,507, 4,772,386 and 4,769,135.
The mechanisms described therein are used in various fields but none of them is suitable for direct application, as in the case of the present invention, to disposable filter cartridges such as those used in jug water purifiers for domestic use.
The main aim of the present invention is to provide a filter cartridge which can be used quite safely for making water drinkable as well as possibly cleansing it of undesired odours and flavours in jug or carafe purifiers for domestic use.
Within the scope of this aim, the object of the invention is to provide a replaceable filter cartridge which can be produced easily and inexpensively so that the device for shutting off the flow of fluid being treated can be incorporated directly in the replaceable cartridge in order to block the cartridge once its filtering capacity is exhausted.
This and other objects are achieved by the invention by means of a filter cartridge formed in accordance with the following claims.